My SO asked for a hall pass

Let me start off with background. I was trouble when i was younger and have had a few partners. My SO has not. I have been his only partner. Im a little over 13 weeks pregnant and we are engaged after almost 5 and a half years. Today he asked when he will get a hall pass so he doesnt live his life sleeping with only one woman..... i didnt get mad bc well one... i have more experience and 2 i didnt know if he was kidding or not.... has anyone ever dealt with this?